Does Blender have a software-limited amount of RAM it can use?
What is memory management (from http://www.tutorialspoint.com/):


  Memory management is the functionality of an operating system which handles or manages primary memory. Memory management keeps track of each and every memory location either it is allocated to some process or it is free. It checks how much memory is to be allocated to processes. It decides which process will get memory at what time. It tracks whenever some memory gets freed or unallocated and correspondingly it updates the status.


There is no software cap. There can't be - it would have to be coded in for it to be. Blender will use all your RAM up to 16TB (64bit). Its up to the OS to provide the memory for blender.

If you have a page file it starts at around 2 GB or 4 GB and windows expands the page file when needed. However, they might not be as fast as Blender requests more memory. If this happens, Windows does not allow Blender to get more RAM and causes an out of memory exception which crashes Blender.

At that point the page file gets bigger and in second run of Blender its very likely everything will run/render without problems.

If your OS fails to allocate some memory for Blender fast enough, Blender will crash.